The present invention relates to a device for conveying lubricant from and to a gear.
The gears, for example the gears in motor vehicles, which are currently available are in most cases lubricated by so-called splash lubrication. This means that the gear housing has an oil sump which is partially filled with oil so that at least one gear wheel is at least partially immersed in the oil. During operation, the gear wheel rotates and oil is therefore splashed up from the sump providing the required lubrication.
This arrangement causes the oil to become increasingly contaminated the longer the gear is in operation, which in turn causes increased wear. In order to reduce this wear, and hence to increase the life of the gear, the oil is changed at suitable intervals during the life of the gear.
One method of extending the life of the gear still further is to arrange a filter on the gear for the purpose of continuously cleaning the oil. This is done today, for example, in some vehicle gearboxes. Such a solution may even allow a longer operating time between the required servicings of the engine, which are both expensive and time consuming. However, such a solution means that the oil must be pumped through the filter by means of a pumping device, which requires an expensive and complicated gear design.
For central gears arranged on the drive shaft of the motor vehicle, the problem is particularly serious because in most cases only splash lubrication is used without any form of filtration.
German published specification DE 40 23 364 shows a design in which the crown wheel of the central gear throws oil up to a reservoir arranged inside the gear housing. The oil is then fed down from the reservoir via pipes for lubricating parts that are difficult to reach, such as hub bearings, from which the oil then returns to the oil sump. According to this design, kinetic energy from the crown wheel is converted by the displacement of the oil to potential energy to allow lubrication. Thus, there is no filtration or other reconditioning of the oil.
The foregoing reasoning also applies to types of lubricating oil reconditioning other than filtration, for example cooling of the oil by allowing it to be fed through an external cooling pipe.
German published specification DE 31 16 595 shows a design for cooling the lubricating oil for the central gear of a vehicle. The design provides a cooling pipe which is arranged partly inside and partly outside the gear housing. The cooling pipe is closed and contains a coolant for cooling the lubricating oil. This solution cannot be adapted to other types of reconditioning because oil does not flow through the cooling pipe.